The present invention relates to a system and method for the treatment of disorders of the vasculature. More specifically, the present invention relates to a system and method for treatment of thoracic or abdominal aortic aneurysm and the like, which is a condition manifested by expansion and weakening of the aorta such conditions require intervention due to severity of the sequelae, which frequently is death. Prior methods of treating aneurysm have consisted of invasive surgical methods with graft placement within the affected vessel as a reinforcing member of the artery. However, such a procedure requires a surgical cut down to access the vessel, which in turn can result in a catastrophic rupture of the aneurysm due to the decreased external pressure from the surrounding organs and tissues, which are moved during the procedure to gain access to the vessel. Accordingly, surgical procedures have a high mortality rate due to the possibility of the rupture discussed above in addition to other factors. Such Other factors can include poor physical condition of the patient due to blood loss, anuria, and low blood pressure associated with the aortic abdominal aneurysm. An example of a surgical procedure is described in a book entitled Surgical Treatment of Aortic Aneurysms by Denton A. Cooley, M. D.,published in 1986 by W. B. Saunders Company.
Due to the inherent risks and complexities of surgical procedures, various attempts have been made in the development of alternative methods for deployment of grafts within aortic aneurysms. One such method is the non-invasive technique of percutaneous delivery by a catheter-based system. Such a method is described in Lawrence, Jr. et al. in xe2x80x9cPercutaneous endovascular graft: experimental evaluationxe2x80x9d, Radiology (May 1987). Lawrence describes therein the use of a Gianturco stent as disclosed in U.S. Pat. No. 4,580,568. The stent is used to position a Dacron(copyright) fabric graft within the vessel. The Dacron graft is compressed within the catheter and then deployed within the vessel to be treated. A similar procedure has also been described by Mirich et al. in xe2x80x9cPercutaneously placed endovascular grafts for Aortic Aneurysms: Feasibility Study,xe2x80x9d Radiology (March 1989). Mirich describes therein a self-expanding metallic structure covered by a nylon fabric, with said structure being anchored by barbs at the proximal and distal ends.
One of the primary deficiencies of the existing percutaneous devices and methods has been that the grafts and the delivery catheters used to deliver the grafts are relatively large in profile, often up to 24 French and greater, and stiff in bending. The large profile and bending stiffness makes delivery through the irregular and tortuous arteries of diseased vessels difficult and risky. In particular, the iliac arteries are often too narrow or irregular for the passage of a percutaneous device. Because of this, non-invasive percutaneous graft delivery for treatment of aortic aneurysm is not available to many patients who would otherwise benefit from it.
What has been needed is an endovascular graft and delivery system for the graft which has a small outer diameter and high flexibility to facilitate percutaneous delivery in patients who require such treatment. What has also been needed is a delivery system for an endovascular graft which is simple, reliable and can accurately deploy an endovascular graft within a patient""s body.
The invention is directed generally to a catheter for delivery of a variety of expandable intracorporeal devices, specifically, an endovascular graft which can be self expanding. The catheter can have an elongate shaft with a proximal section, a distal section, a proximal end and a distal end. The distal section of the elongate shaft can have a radially expandable shear barrier disposed about an inner space which is configured to accept an expandable intracorporeal device in a collapsed state. The catheter can be used for delivery and deployment of any appropriate expandable intracorporeal device. Typically, the catheter is used to deliver and deploy an expandable endovascular device such as a graft or stent graft. An outer radially constraining section is disposed about and radially constraining at least a portion of the radially expandable shear barrier and is capable of axial movement relative to the radially expandable shear barrier so as to controllably remove the radial constraint and allow the expandable intracorporeal device to deploy. Typically, the catheter is configured for percutaneous delivery from outside a patient to a desired site within a patient""s body through an intracorporeal conduit or tissue of the patient.
In one embodiment, the radially expandable shear barrier and the outer radially constraining section are mechanically coupled to at least one terminal member disposed at the proximal end of the elongate shaft such that relative axial movement of the radially expandable shear barrier and outer radially constraining section can be carried out by an operator manipulating the terminal member at the proximal end of the elongate shaft. An actuator can be mechanically coupled to the at least one terminal member such that controllable and automatic relative axial movement between the radially expandable shear barrier and outer radially constraining section of the distal section of the elongate shaft can be carried out by activation of the actuator.
In another embodiment, the radially expandable shear barrier is in the form of a slitted inner tubular section having a generally tubular configuration and a distal end with at least one longitudinal slit extending proximally from the distal end. The slitted inner tubular member has an inner lumen disposed within it which is configured to accept at least a portion of an expandable intracorporeal device in a collapsed state. An outer tubular section is disposed about and radially constrains at least a portion of the slitted inner tubular section. The outer tubular section is capable of axial movement relative to the slitted inner tubular section in order to remove the radial constraint and allow the expandable intracorporeal device to deploy. The slitted inner tubular section and the outer tubular section can be mechanically coupled to at least one terminal member disposed at the proximal end of the elongate shaft such that relative movement of the inner and outer tubular sections can be carried out by an operator manipulating the at least one terminal member at the proximal end of the elongate shaft. Alternatively, the slitted inner tubular section can be mechanically coupled to a first terminal member consisting of a proximal handle disposed at the proximal end of the elongate shaft. The outer tubular section can be mechanically coupled to a second terminal member consisting of a distal handle disposed at the proximal end of the elongate shaft. Relative movement between the slitted inner tubular section and the outer tubular section can be carried out by imparting relative axial movement on the proximal and distal handles.
In yet another embodiment, a guidewire tube is disposed within the inner lumen of the slitted inner tubular section and has an inner guidewire lumen, a proximal end, a distal end and a distal section. A distally tapered nose piece can be disposed about and secured to the distal section of the guidewire tube. Optionally, the nosepiece disposed about a distal section of the guidewire tube can have a distal end with a contoured distally tapered bullet shape. The nosepiece can have a proximal end which is configured to engage the inner lumen of the distal end of the outer tubular section and produce a substantially smooth outer surface at the junction between the distal end of the outer tubular section and the nose piece.
The invention is also directed to a method for deploying an expandable intracorporeal device within a patient""s body. A catheter system suitable for use with the method has an elongate shaft having a proximal section, a distal section, a proximal end and a distal end. The distal section of the elongate shaft has a radially expandable shear barrier disposed about an inner space configured to accept the expandable intracorporeal device in a collapsed state. An outer radially constraining section is disposed about and radially constrains at least a portion of the radially expandable shear barrier and which is capable of axial movement relative to the radially expandable shear barrier member in order to remove the radial constraint and allow the expandable intracorporeal device to deploy.
An expandable intracorporeal device is disposed within the inner space of the radially expandable shear barrier. As discussed above, such a catheter can be used for delivery and deployment of any appropriate expandable intracorporeal device. Typically, the catheter is used to deliver and deploy an expandable endovascular device such as a graft or stent graft. The distal end of the catheter system is introduced into the patient""s body and advanced to a desired site within the patient""s body. Various forms of guidance are suitable, including advancing the catheter over a guidewire or the use of a deflecting or steerable distal tip on the catheter. The catheter can be imaged during the procedure with fluoroscopic imaging, MRI, ultrasound or any other suitable form of imaging. In order to facilitate such imaging techniques, it may be desirable to place markers on the catheter or expandable intracoporeal device that enhance such techniques, such as radiopaque markers, ultrasound enhancement markers, isotopes or the like.
Once the distal section of the catheter and collapsed expandable intracorporeal device disposed within the catheter are located in a desired position, the expandable intracorporeal device is deployed. Deployment of the expandable intracorporeal device can be carried out in one embodiment of the invention by initiating relative axial movement between the radially expandable shear barrier and the outer constraining section. The relative movement sequentially removes the radial constraint on the radially expandable shear barrier to allow the expandable intracorporeal device to expand and deploy at the desired site.
In another embodiment of the method, a catheter is used wherein the radially expandable shear barrier is in the form of a slitted tubular section and the outer radially constraining section comprises an outer tubular section. Relative axial movement between the slitted inner tubular section and the outer tubular section can be carried out by axially withdrawing the outer tubular section from the slitted tubular section in a proximal direction. In addition, it may be desirable to deploy an expandable intracorporeal device which is an expandable endovascular graft having an expandable anchor portion disposed at a longitudinal extremity of the graft. With such a graft, the expandable anchor portion can be disposed within an inner lumen of the outer tubular section distal of a distal end of the slitted inner tubular section prior to deployment. Initiation of relative axial movement between the slitted inner tubular section and the outer tubular section can then be carried out to first relieve radial constraint on the expandable anchor portion and then sequentially the slitted inner tubular section.